[Definition of obesity in childhood: criteria and limits]

A rigorous scientific definition of obesity in childhood is not yet available: in fact, there is not agreement among researchers on the adiposity index to use and on the best cut-off to define overweight and obesity. In this review, the reference methods for the diagnosis of childhood obesity in the clinical practice in Italy are reported. All the statements are based on evidences of the literature and obtained the consensus of the pediatricians of the Study Group on Obesity of the Italian Society of Pediatric Diabetology and Endocrinology. Obesity is caused by an excess of body fat. The methods more frequently used to measure body fat are the measure of subcutaneous skinfold thickness, bioimpedence assessment and DXA. The measure of skinfolds is preferable in the clinical setting because it is easy to use and cheap, although reproducibility is modest. Triceps skinfold is commonly used to define obesity: children with triceps higher than the 85(th) centile for age and gender, using Tanner's tables, are obese. An estimation of fat mass obtained, for instance, with skinfolds is always suggested in addition to the measure of weight and height. It is possible to define a child as obese calculating the ratio between weight (kg) and height squared (m). This ratio is an index, called body mass index (BMI), which is strictly associated to the level of adiposity in children, reproducible and valid. The BMI was recently proposed as the reference index for the diagnosis of childhood obesity at the international level. The use of the centiles of BMI may offer useful information on the changes of weight excess, simplifying the follow-up of the patient and the sensitivity to treatment. The cut-off limits of BMI to define overweight or obesity are still debated. However, in agreement with Cole et al., the choice to use the BMI cut-offs centiles passing through the adult BMI cut-off of 30, is reasonable. However, it is always preferable to use population specific BMI reference tables.